Coring bit



y 1962 L. J. ELZEY 3,032,130

CORING BIT Filed Oct. 18, 1957 2 Sheets-Sheet 1 FIG.'|

Lloyd Joy Elzey Inventor Attorney May 1, 1962 1.. .1. ELZEY 3,032,130

CORING BIT Filed Oct. 18, 1957 2 Sheets-Sheet 2 /&

Lloyd Joy Elzey Inventor WW4. Attorney United States Patent Q 3,032,130 CORING BIT Lloyd J. Elzey, 820 N. Florence, Tulsa, Okla. Filed Oct. 18, 1957, Ser. No. 690,982 5 Claims. (Cl. 175403) This invention generally pertains to coring apparatus and more particularly to an improved type of coring bit. The invention has application to the coring of subterranean strata generally, and it is especially suited for rotary coring as practiced in petroleum exploration and drilling operations.

Coring procedures and apparatus are well known as such in the art and find extensive use in the search for minerals such as uranium, nickel, silver etc. They also find particular application by the petroleum industry in the search for oil. The data that'are obtained from core samples of subterranean formations aid greatly in locating and evaluating many forms of mineral deposits. In the production of petroleum, the data are very helpful in determining the best procedure for recovering additional quantities of oil from a known reservoir.

Several types of coring tools and systems are employed in the general art. The type of particular concern to the present invention, however, is the rotary type which uses a rock bit mounted on the lower end of a string of drill pipe. The design of the bit is such that, as the drill pipe is rotated, the bit makes an annular cut. The core left by the cut is recovered by allowing the core to pass up through the bit into a core barrel.

A wide variety of core barrels are available and employed in conjunction with coring bits to receive and retain a core sample after it has been cut by a bit. While a core barrel is a vital part of any coring tool, it is the bitand not the barrelportion of coring tools with which the present invention is directly concerned. Accordingly, this description is directed primarily toward bits and not toward core barrels or other components of conventional coring systems.

As mentioned above, rotary coring bits are generally characterized by their ability to generate an annular-type out within the earth. Some bits make use of a plurality of cutter elements that are spaced around the periphery of the bit, while other bits have a single continuous cutting surface extending around the bit. The latter type generally uses hardened steel teeth, diamond particles, various carbide alloys, etc., which are embedded within the surface of the bit.

One of the great problems confronted in present rotary coring operations is one of obtaining substantially complete core recovery. It is well recognized in the art that it is frequently difficult to core continuously through a subterranean structure without unduly breaking, losing, or disturbing the orientation of a core. This is particularly true when operating in unconsolidated or striated structures, in friable rock, or where different cleavage planes are encountered.

Associated with the problem of obtaining more complete core recovery is the problem of obtaining a core on the first attempt. Coring and drilling are expensive operations, and unsuccessful elforts at taking a core are to be avoided as much as possible.

It is, accordingly, an object of this invention to provide an improved means for obtaining core samples. More particularly, it is an object of the invention to provide a coring tool with a bit which enables the tool to achieve greater core recoveries.

These and related objects, which will be explicity described or readily apparent in the following description, are realized in accordance with this invention by means of a bit which is both smooth-running and possessed of 3,032,130 Patented May 1, 1962 limited rock penetration. The bit is a multi-cutter one, the cutters being spaced around the periphery of the bit. The leading or cutting edge of each cutter element is preferably provided with abrasive particles such as diamonds, carbide alloys, and the like to provide the necessary cutting action.

In vertical cross section-i.e., in a section taken vertically and along a radius of the biteach cutter element presents a concave contour along its lower or trailing surface. Expressed otherwise, the leading or cutting edge of each cutter element is concave so that its inner and outer peripheral boundaries extend lower than the central portion of the edge. This concave characteristic of the cutter element extends backwardly from the leading edge of the element toward the trailing edge. Furthermore, the trailing or lower surface of each cutter element slopes gradually upward, i.e., toward the body of the bit, and away from the leading edge.

Spaced arcuately behind the leading edge of each cutter element is a roller element whose axis is generally perpendicular to the direction of bit rotation. Each roller element is recessed and mounted within its cutter element so that a relatively small portion of its rolling surface projects below the lower surface of the element but above the surface of the cuttingor leading-edge. Additionally, the rolling surface of each roller is contoured along its length to present the same general concave appearance as the under surface of its cutter element. Thus, as the bit is rotated, the leading edge of each cutter element cuts into an earthen formation; but the depth of cut is automatically regulated by the vertical distance between the cutting edge of the element and the rolling surface of its respective roller member. Expressed otherwise, the roller member automatically limits the depth of cut of its cutter element and yet-by virtue of its rolling nature does so with a minimum of friction and rubbing.

It is a particular feature of the bits of this invention that greater bit loadings can be used than with conventional coring bits. Conventional bits, by being pressurelimited, tend to allow cuttings to pass under them and damage or even ruin core samples. The bits of the invention, on the other hand, avoid this difficulty by maintaining improved contact with an underlying formation.

The bits of the invention-by virtue of their greater loadings and their contoured cutting elements-also reduce the degree of whip or horizontal slip that characterizes the performance of conventional bits. The concave construction of the lower or trailing surface of each cutting element as well as the matching contour of its roller acts as a bearing surface to minimize lateral deviations of a hit.

As with many conventional bits, the bits of this invention are provided with fluid passageways which enable drilling mud or other drilling fluid to remove cuttings from the vicinity of the cutting elements and to carry the cuttings up the borehole.

The nature of the invention may be better understood by reference to the attached drawing in which:

FIGURE 1 is a bottom view of a multi-cutter bit which constitutes a preferred embodiment of the invention.

FIGURE 2 is a vertical section view of the apparatus of FIGURE 1 taken along the section lines 2-2 of FIGURE 1.

FIGURE 3 is a vertical section taken along the section line 3-3 of FIGURE 1.

FIGURE 4 is a section view of a roller showing added details of the roller.

FIGURE 5 shows a vertical section of the type of hole cut by the bits of the invention.

FIGURE 6 is a side view of the apparatus of FIGURE 1, slightly cut away.

Referring to the figures, it will be seen that the major components of the structure shown include a body 20, cutter elements 21, core passageway 22, rollers 23, threaded pin portion 24, drilling-fluid passageway 25, and ports 26.

As shown in the figures, the cutter elements 21 are equally spaced around the periphery of the bit. The elements 21 are generally wedge-shaped and may be formed integral with body 20 as by forging. As will be further apparent from the figures, the bit is adapted for clockwise rotation as conventionally viewed from the top of a borehole. As viewed from the bottom of a borehole as in FIGURE 1, the direction of rotation would actually appear to be counterclockwise.

The cutting or leading edge 42 of the leading surface 49 of each cutter element is contoured transversely in a concave manner. The lower trailing surface 44 of each cutter element also has a concave transverse contour; and it is tapered from the leading edge 42 toward the trailing edge 43 so that the leading edge is lower than the trailing edge when the bit is in a drilling position. This structure is especially suited to effect a very stableand smooth-running type of action for the bit.

Referring in detail to the lateral or radial contour of the cutter elements, it is generally desirable that one peripheral boundary of the element project downward somewhat farther than the other boundary. As particularly shown in FIGURE 2 and FIGURE 3, the outer boundary 46 extends downward beyond the inner boundary 47.

As shown particularly in FIGURE 2, the lower surface 44 of each cutter element slopes upwardly from the leading edge 42 toward the trailing edge 43 of the element. Spaced from and between the leading and trailing edges is a roller 23 which has a contour along its periphery which corresponds to the radial or transverse profile of the lower surface of its cutter element. As also shown particularly in FIGURE 2, each roller is mounted within its respective cutter element so as to project slightly down and beyond the adjacent lower surface 44 of the cutter element. It does not, however, project downward beyond the leading edge 42 of the cutter element. The roller therefore limits the depth of cut that the leading edge may take in any given instance. Its rolling contact also enables this limiting action of the roller to be realized with a minimum of friction or resistance. The roller is preferably constructed of a hard, tough steel or other alloy' of a character to resist wear.

At this point, it should be noted that, if so desired, each roller may comprise a plurality of small rollers arranged side-by-side rather than a single roller. It will further be recognized that rollers will not be necessary in coring all types of structures-especially very soft ones. In such instances, the concave and sloping trailing surfaces of the cutter elements themselves may be used to effect control of the depth of cut taken by the leading edges of the elements.

The threaded pin 24 of the bit enables it to be connected to the lower end of other conventional units of well equipment. It is particularly contemplated that the bits of this invention will be threadedly connected to the lower end of the outer barrel of a conventional core barrel. Conventional core barrels generally comprise a rotating outer barrel, such as barrel 30 in FIGURE 3, and a stationary inner barrel such as barrel 31. The inner barrel in FIGURE 3 it will be observed, effects a liquid seal with the shoulder 32 which extends around the inner periphery of the bit structure. This relationship between the bit and the inner and outer barrels enables the bit to rotate with the outer barrel while the inner barrel remains stationary. Assemblies of this type, it will be noted, have already been described and used in the art. (See, for example, the Type I coring tools illustrated on pages 2494 and 2495 of the 1957 edition of the Composite Catalog of Oil Field Equipment and Services, Volume 2'.)

The port arrangement in the present bits enables drilling mud or other drilling fluid, which conventionally flows downward within the annular space 34 between the inner and outer barrels of a coring tool, to flow through the central fluid passageway 25 and the ports 26 of the coring bit of this invention. As shown in the attached figures, passageway 25 is preferably an annular-type passageway extending around the body of the bit. The ports 26 lead from passageway 25 to points in the vicinity of the cutting portions of the cutter elements. Drilling rnud is therefore discharged from the ports in a manner to aid the drilling action by flushing drill cuttings from the cutter elements.

The leading, or cutting, edge of each cutter element may in some instances be formed simplyof a hardened steel. In such cases, the bits of this invention resemble drag bits and are particularly suited for use in very soft or striated formations.

When relatively hard formations are to be cored, the leading or cutting edge of each cutter element may be provided with diamonds or particles of hard abrasive materials such as Carborundum, tungsten carbide, and the like.

The rollers of the invention may be installed within thecutter elements in any suitable manner. One manner contemplated to be especially effective is that shown in FIGURE 4. The roller in that instance is mounted upon and is free to revolve with shaft 33 which is mounted at each end in suitable bearings.

Having set forth and described the structural features of the bit shown in the attached figures, consideration is now given toward themanner in which the bit may be operated. Thus, as shown in FIGURE 3, the bit is attached tothe lower end of the outer barrel 30 of a conventional core barrel. It is then lowered within a borehole until it approaches contact with a formation of interest. Drilling fluidgenerally drilling mutis pumped down through the drill string and then through the annular passageway 34 between the inner and outer barrels of the core barrel until it reaches the passageway 25. It then flows down through the ports 26, where it issues from the bit and circulates up between the drilling equipment and the borehole to the surface of the earth.

When circulation of drilling mud has been attained, the bit and the drill string are rotated; and the bit is engaged against the formation. As the cutter elements cut into the formation, the resulting cuttings are flushed from the bit by means of the drilling mud. The cutting edges or portions of the cutter elements are prevented from taking an undesirably deep cut by virtue of the rollers 23 and trailing portions 44 of the cutter elements which follow in the wake of the cutting edges. Thus, as the bit revolves, the cutting edges or portions 42 of the cutter elements are prevented from taking any more than a predetermined depth of cut from an underlying formation. The resulting core passes up through the passageway 22 and is received within the inner barrel 31 of the core barrel. The coring process is continued until the desired amount of formation has been penetrated. At this point, the coring process is interrupted, the core is parted in a conventional manner, and the entire apparatus is removed from the borehole. A conventional core catcher may be used to retain the core within the inner barrel.

In those instances where is is desirable to use different depths of cut, it will be recognized that it is readily possible to change the diameter of the roller elements 23. Rollers of relatively large diameter may be used where small depths of cut are preferred; and, conversely, rollers of relatively small diameter may be used where relatively large depths of cut are desirable.

As noted earlier in this description, FIGURE 5 shows a vertical section or profile of the type of hole which is cut by a bit of this invention. Referring to the figure, the legend 37 depicts the point or level within a borehole 36 from which a coring operation has been carried out using a tool of this invention. The annular cut 40 was made by the bit, leaving a central core 41 of the formation material 38. The convex, crown-like shape of the surfaces 39 will be especially noted.

While the specific embodiment of the invention which has been described above and illustrated in the attached drawing is considered to be a preferred embodiment of the invention, it Will be recognized that the embodiment is subject to a number of modifications, deletions, and changes without departing from the spirit or scope of the invention.

The invention claimed is:

1. A rotary coring bit which comprises a body member having an upper end and a lower end and a longitudinally and centrally disposed core passageway for the passage of a core therethrough, a plurality of cutter elements on the lower end of said body member positioned around said core passageway, each cutter element having a radially disposed leading surface extending below said body member and terminating in a concave cutting edge, each cutter element also having a lower concave trailing surface sloping upward from said cutting edge, and drillingfluid passageway means extending longitudinally through said body member and arranged to discharge drilling fluid in the vicinity of each cutter element.

2. A coring bit as defined in claim 1 in which each cutter element has a recess projecting upward from the trailing surface thereof, a roller member positioned within each said recess and journalled within its respective cutter element with its longitudinal axis in a radial disposition relative to said body member, each roller member projecting below the trailing surface of its respective cutter element and being displaced upwardly from the cutting edge thereof.

3. A rotary coring bit including a body member with upper and lower ends and an axially disposed core passageway extending longitudinally therethrough, the upper end of said coring bit adapted to be secured to the lower end of a drill string, a plurality of cutter elements on the lower end of said body member and positioned around said core passageway, each cutter element having a leading concave cutting edge arranged transversely to the direction of rotation of the hit, each cutter element also having a lower trailing surface concave to correspond to its respective cutting edge and sloping upward therefrom, and fluid passageway means extending throughout the length of said body member to transmit drilling fluid from Within said drill string to the vicinity of said cutter elements.

4. A rotary bit as defined in claim 3 in which each cutter element has a recess projecting upward from its respective trailing surface, a roller member positioned within each recess and journalled within its cutter element such that its longitudinal axis is generally transverse to the direction of bit rotation, each roller member having a longitudinal contour resembling the concave contour of the trailing surface and of the cutting edge of its respective cutter element, each roller member also pro jecting from its recess below the trailing surface of its respective cutter element and displaced upwardly from the cutting edge thereof.

5. A rotary coring bit adapted to be secured to the lower end of a drill string which comprises a body member having upper and lower ends and a core passageway extending throughout and along the longitudinal axis of said body member, a plurality of cutter elements on the lower end of said body member disposed around said core passageway, the lower and leading extremity of each cutter element defining a concave cutting edge lying transverse to the direction of bit rotation, each cutter element also having a lower surface which is concave to correspond to its respective cutting edge and which slopes upward therefrom, and fluid passageway means extending throughout the length of said body member to convey drilling fluid from said drill string to the vicinity of each, cutter element.

References Cited in the file of this patent UNITED STATES PATENTS 659,139 Eagen Oct. 2, 1900 1,015,446 Knapp Jan. 23, 1912 1,850,358 Scott Mar. 22, 1932 1,923,488 Howard et a1 Aug. 22, 1933 2,641,447 Kammerer June 9, 1953 2,729,427 Davis et al. Jan. 3, 1956 2,756,024 McDonald July 24, 1956 2,818,233 Williams Dec. 31, 1957 2,819,043 Henderson Jan. 7, 1958 2,854,219 MacNeil Sept. 30, 1958 

